Poisons on public lands put wildlife at risk (w/ Video)

July 13, 2012

Rat poison used on illegal marijuana farms may be sickening and killing the fisher, a rare forest carnivore that makes its home in some of the most remote areas of California, according to a team of researchers led by University of California, Davis, veterinary scientists.

Researchers discovered commercial rodenticide in dead fishers in Humboldt County near Redwood National Park and in the southern Sierra Nevada in and around Yosemite National Park. The study, published July 13 in the journal PLoS ONE, says illegal marijuana farms are a likely source. Some marijuana growers apply the poisons to deter a wide range of animals from encroaching on their crops.

Fishers, a member of the weasel family, likely become exposed to the rat poison when eating animals that have ingested it. The fishers also may consume rodenticides directly, drawn by the bacon, cheese and peanut butter "flavorizers" that manufacturers add to the poisons.

Other species, including martens, spotted owls, and Sierra Nevada red foxes, may be at risk from the poison, as well.

In addition to UC Davis, the study involved researchers from the nonprofit Integral Ecology Research Center, UC Berkeley, United States Forest Service, Wildlife Conservation Society, Hoopa Tribal Forestry, and California Department of Fish and Game.

The video will load shortly

"Our findings were very surprising since non-target poisoning from these chemicals is typically seen in wildlife in urban or agricultural settings," said lead author Mourad Gabriel, a UC Davis Veterinary Genetics Laboratory researcher and president of the Integral Ecology Research Center. "In California, fishers inhabit mature forests within the national forest, national parks, private industrial and tribal community lands  nowhere near urban or agricultural areas."

Researchers analyzed 58 fisher carcasses and discovered that 79 percent of them had been exposed to anticoagulant rodenticides. Brodifacoum, a second-generation rodenticide, was found in 96 percent of the exposed fishers.

Second-generation rodenticides are more toxic because they can be lethal after a single ingestion. It can take up to seven days before clinical signs appear, so the poisoned animal can be a significant risk to predators for several days before it dies.

"I am really shocked by the number of fishers that have been exposed to significant levels of multiple second-generation anticoagulant rodenticides," said pathologist Leslie Woods of the UC Davis California Animal Health and Food Safety Laboratory System, which conducted the necropsies.

Anticoagulant rodenticides inhibit the ability of fishers and other mammals to recycle vitamin K. This creates a series of clotting and coagulation problems, which may lead to uncontrollable bleeding.

Exposure to the poison was high throughout the fisher populations studied, complicating efforts to pinpoint direct sources. The fishers, many of which had been radio-tracked throughout their lives, did not wander into urban or agricultural environments. However, their habitat did overlap with illegal marijuana farms.

The researchers describe a recent example in which more than 2,000 marijuana plants were removed by law enforcement officials less than 7.5 miles from one of the study areas. Large amounts of rodenticide were observed around the marijuana plants and along plastic irrigation lines.

The fisher deaths occurred between mid-April to mid-May, the optimal time for planting young marijuana plants outdoors -- and the time when seedlings are especially vulnerable to pests. This is also when fishers are breeding and raising their young.

Gabriel said fishers may be an "umbrella" species for other forest carnivores. In ecology, an umbrella species is one that, if protected, results in protection of other species, as well.

"If fishers are at risk, these other species are most likely at risk because they share the same prey and the same habitat," said Gabriel. "Our next steps are to examine whether toxicants used at illegal marijuana grow sites on public lands are also indirectly impacting fisher populations and other forest carnivores through prey depletion."

Related Stories

U.S. Forest Service and U.C. Santa Barbara scientists believe they have identified the habitat needs for Pacific fishers, a rare California mammal that is a candidate for reintroduction efforts and listing under the Endangered ...

(PhysOrg.com) -- A University of California wildlife research team working in the Sierra Nevada is asking the public to donate clean, gently used socks for research on a rare weasel called the Pacific fisher.

The Hoopa Valley Tribe, in cooperation with the Wildlife Conservation Society and the University of Massachusetts, reported a 73-percent decline in the density of fishersa house-cat sized member of the weasel family ...

Rats might not be everyone's cup of tea, but you might want to think twice about reaching for the rat poison next time you come across one. While rat poison is brilliant at killing rats, it also spells danger for a whole ...

Hunted to near extinction, sea otters are making a steady comeback along the Pacific coast. Their reintroduction, however, is expected to reduce the numbers of several key species of commercially valuable shellfish dramatically, ...

Recommended for you

(Phys.org)—That there are universal patterns in the naming of colors across languages has long been a topic of discussion in a range of disciplines, including anthropology, cognitive science and linguistics. However, previous ...

(Phys.org)—A team of researchers with members from several institutions in China has calculated what they believe is the minimum amount of land preservation needed to sustain wild giant panda populations. In their paper ...

The differences in how male and female fruit flies resist and adapt to oxidative stress may shed new light on how age-related diseases such as Alzheimer's and Parkinson's affect men and women differently.

Many infectious pathogens are difficult to treat because they develop into biofilms, layers of metabolically active but slowly growing bacteria embedded in a protective layer of slime, which are inherently more resistant ...

Researchers have discovered a way to program cells to inhibit CRISPR-Cas9 activity. "Anti-CRISPR" proteins had previously been isolated from viruses that infect bacteria, but now University of Toronto and University of Massachusetts ...

9 comments

I wonder if rats or (I'm guessing) generic small rodents are particularly attracted to marijuana, or just whatever small seedlings are available?I'm not a big fan of poison bait. I had been using it for a mouse problem in my garage. It would get eaten (I had to replace the bait bars frequently), but the mouse problem persisted. I think rodents can figure out how to eat sub-lethal amounts. Also, it turns out the poison used in the brand of bait I used, bromethalin, has no antidote. If poisoned, corticosteroids have to be administered for the rest of the victim's life. I don't like having stuff like that around.I went on to use a variation on the plain old spring-loaded jaw trap. It's worked well. Mouse problem dealt with, and no poison.

how will legalizing weed stop the farmers from putting poisons on to protect it? if anything it would make the problem of these poor animals dying worse because more people would grow weed equalling more poison and you fill in the rest

Legalising means they wont have to grow out in the forest, hence no poison to kill wild animals.

The demand for marijuana could be satisfied by the LEGAL outlets, making profits from illegal grows smaller. Make grows in forests an extreme crime, but buying from LEGAL shops completely safe. Legal outlets also wont have rat poison contaminated plants either!!!

I just don't understand the illegal stance on marijuana. Currently it's illegal, and yet how much of the stuff is being produced???? None of it taxed of course. How much money is being spent on searching for the stuff and busts??? It's prohibition, simple!!!

I'll also add, how many people have you seen get into fights, after they have smoked marijuana?? Now compare that with the violence associated with alcohol. Legalising also allows for consumers of marijuana to be educated. Yes SOME people may go psycho, but those people are probably predispositioned to that anyway, and any trigger could activate it. Any pyschotic episode is also temperary!!!! Think about it!!! Thats why legalisation and education would allow health experts such as doctors to give advice to those whoe consume it.

If marijuana is as deadly as the Government would have you think, then if I ever end up on death row, I'm gonna choose death by marijuana smoking as apposed to lethal injection!!!